### Please describe the problem.

The checkpresent endpoint (and also less importantly the gettimestamp endpoint) of the p2phttp protocol is specified to use POST, when what it does is really a GET request for the presence information without any mutation of data warranting a POST. In the dumb http realm this function is served by a HEAD request for the file, which is conceptually also a GET, just without the actual data.

In forgejo-aneksajo there is a blanket authentication requiring read permissions for all GETs and write/admin permissions for all POSTs (or anything other than GET, really), so right now I have to special case checkpresent while it would just do the right thing if checkpresent was a GET.

This isn't really a problem, just a bit of an annoyance.

### What steps will reproduce the problem?


### What version of git-annex are you using? On what operating system?


### Please provide any additional information below.

[[!format sh """
# If you can, paste a complete transcript of the problem occurring here.
# If the problem is with the git-annex assistant, paste in .git/annex/daemon.log


# End of transcript or log.
"""]]

### Have you had any luck using git-annex before? (Sometimes we get tired of reading bug reports all day and a lil' positive end note does wonders)


